E DESIGN 



F 1 1 R M A N 




Gass TT 5IS1 
Book F^ 



NOTES ON 

ENGINE DESIGN 






BY 

FRANKLIN DeR. FURMAN.3 M.E. 

PBOFB88OB OP MECHANISM IND MACHINE DESIGN 
3TE1 RNS [N8 i i PI I i 01 I i < BNOLOGT 



HOBOKEN, N. .1. 

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Copyright, 1911, by 
FRANKLIN DeR. FURMAN 



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THE TROW PRESS 
NEW YORK 






©CLA303010 



P R EFAC E 

3€ aotea have to do with an elementary problem in engine design. No specific data are 
□ ; the student musl choose his own, assuming numerals to represent the horse-power, I he revo- 
lutions per minute, and the boiler-pressure. 

As the practical engineer knew- wn well, there are certain standard relations between the 

numerals that may be here chosen. It has been found, however, thai although these relation- may 

told over and over again, that one does not fully realize thai there is, for example, a limiting piston 

d establishing a relation between length of st poke and revolutions per minute, and establishing 

a limit of inertia of moving parts which results in certain relations between horse-power and 

olutions per minute, until one has run up againsl the actual obstruction himself. 

In requiring the beginner to assume his own data, he is quite likely to assume an impracticable 

combination, ami it is some advantage for him to do so, for these notes are so arranged that he can- 
not spend much time before coming face to face with the consequences of a wrong assumption, 

when another start will give him an experience and an impression that is more likely to l>e of per- 
manent value than if he had assumed correct data the first time. It is quite possible to make three 
or four false starts, each of which will shortly lead to a stopping point in the notes and compels 
new -tart. Xo one can follow through these notes to page <) without having assumed proper data. 

This problem is not intended for a finished exercise in large or complicated mult i-eylindcr design, 

hut it is complete in the elementary work of engine design so far as the cylinder, valve, -team cl 

and stuffing-boxes, etc.. are concerned. Time is too Limited, except in some special cases, to follow 

;L r h the detail design of the crosshead, -haft, crank, frame and bearings, etc., but when there 

is time one of the standard reference books, such as Unwin or Kent, is used for direction. These 

re required of all students, although not for this particular problem, in their 

m I'nwin's Machine Design. 

method of approaching this problem, a- here given, is original is known to the 

writ of the very satisfactory results obtained from it in the course of work in the 

om that ti. are issued in the present form. 

. 1 i:\\ki.i\ I )i \l. Ii k\ia\. 

S .1 . August 18, rui. 



TABLE OF I ONTENTS 



ON I. I INOIN] i R'S 1 h SIGN 

[ntroductioD ... 

Selection of T\ pe 

Procedure in < leneral 
Data for Problem Described in these Note* 

Relations Between Rotativ< Speed, Length of Stroke and H rsr-Power 
P ston Speeds for Various < Classes of Engines 

sed in I )itYnvnt T\ pes of Engines 
aula for Borse-Power of Engine 
Construction of Theoretical Indicator Card 

Determining Initial Steam Pressure from Boiler Pressure ... 

Linear Clearance Distinguished from Steam Clearance 

'■ essure and ( Compression 

Etelation Between Actual and Theoretical Mean Effective Pressures 

Detail of Indicator Card Construction 

Between Length of Stroke and Diameter of Cylinder 

rying Point of Cut-off and Pi-ton Speed Between Narrow Limits to EG 
Bore in Round Numbers and to Maintain Rotative si 

Drafts*) in's Design 

Problem as Obtained from Engineer's Design 

nee on I details of Steam* I design .... 

Formulae Given by Differenl Authors or Such Discrepancy 

and How to Meel Them 

Locations and Center-lines for the Several Views .... 

liminary < lomputal ion 

• hand Sketch to Approximate Scale of ' leneral Outlines of the Parts 

P stons and Piston-rods 

Piston-rod Ends Materials or Long and Short I 



portions for Pistons .... 

Pistons .... . .... 



portions 
Cylinder Wall Thickness 
mterbore 

I ttmensions of Steam Port 

g and Width of ( \ Under I lange 

Mel h i ■•- i Pacing Flai 3 

I Head to Cylinder I ? dumber and Location 



p \-.i 
l 
l 
1 
I 
i 
1 



,p 



iston 



8 

8 

. in 12 

.11,12 

L2 

12 

12 
L2 
13 
13 
L3 
I l 



vi CONTENTS 

Section II. — Draftsman's Design — (Continued) PAGE . 

Cylinder Head Proportions . 14 

Thickness of Cylinder-head Flange . . 14 

Form, Location, and Thickness of Cylinder-head Body for Head and Crank Ends . 14 
Table of Piston (Linear) Clearances for Vertical and Horizontal Engines .... 14 

Stuffing-box for Piston Rod 15-18 

Forms and Proportions for Stuffing-boxes, Glands, and Bushings 16, 17 

Forms of Packing for Stuffing-boxes 16, 18 

Table of Principal Stuffing-box Proportions for Different Diameters of Rod ... 17 

Height, or Location, of Valve Seat 18 

Effect of Exhaust Passageway, Location of Exhaust Pipe, Size of Exhaust Tap and 

Position of Eccentric on Location of Valve Seat 18 

Construction of Plain D- Valve to Give Theoretical Indicator Card Already Found 19 

Sizes and Locations of Exhaust Passageway and Exhaust Pipe 19, 20 

Steam-chest Forms 20 

Thickness of Steam-chest Walls and Flanges 20 

Height of Steam-chest 20 

Width of Flanges and Number and Size of Bolts 20 

Steam-chest Cover 20 

Valve-stem Diameter 21 

Valve-stem Stuffing-box — Forms and Sizes 21 

Size and Location of Live-steam Pipe 21 

Method of Finishing Drawing . .21 



NOTES ON ENGINE DESIGN. 



SECTION 1. ENGINEER'S DESIGN. 

1. Bteam-engine design, considered as a problem in Machine Design, starts with the diameter 
j Under, length of Btroke, revolutions per minute, and initial steam pressure given. Also it must 

be known, of course, whether the engine is Bingle or double acting and if it is a Bingle, double, triple, 
or quadruple cylinder engine. 

2. The selection of type and determination of the data as mentioned above is the busini 

eer, and depends on the nature of the Bervice and the degree of economy required. The 
nature of the Bervice will usually determine t he rotative speed of t he engine -haft , t his ranging from 
very high aa in driving steamship propellers and dynamos, through medium speeds, down to very 
low >p< >d for pump work. The degree of economy obtained depends principally upon t he ral i< 
initial to terminal steam pressure, and the greatest range ie obtained through multiple-cylinder 

isually with simple valves and valve-gears; or, where t he large horse-power of I he multiple- 
cylinder engines ia n<»t required, through a single cylinder engine with a special form of valve or 
valve-gear, or both, that will give an early cut-off and t hue give a large range of expansion. 

method of procedure in the design of a steam-engine aa a machine ia fundamentally the 
e in all typ s. iaaiiming ;i knowledge of thermodynamics of the steam-engine, and of valvea 
and valve-gears that will give any cut-off to meet desired conditions, we will proceed to lay <>ut the 
• steam-engine of the single cylinder, double-acting plain D-valve type, as per- 
mitting the quickest progress, although not giving by any means the greatest economy. The 
directions, however, will be general bo that they could be used for any type of engine were there 
sufficient time to develop the more economical t> | 

L The usual starting point m-engine design is the horse-power and the Dumber of 

olutions per minute. If the engine ia to be installed in a plant where there ia already sufficient 

boiler capacity to take care of it then that boiler pressure must be also included in the data ; or if a 

1 >oil<T is to be in.- tailed to run the engine, the engineer baa greater freedom in detennining the initial 

on —ure. In this problem, data are to be assumed from the following ranges: Borse- 

p<>\. 00; revolutions per minute 160 to MX); and boiler pressure 80 to LOO lbs. above at moe- 

inning up to L25 r.pjn. may be termed low -peed engini 9; those from L25 to 250 
mi., medium Bpeed; and those above 250 r.p.m., high speed. The ranges here given for low, 
lium. and high Bpeed are imi according to :tn\ accepted standard, for, what may be high in one 
line of industrial work may be 1<>w in another. The figures here given are arbitrarily taken, but 
it is believed they are fairly close to the broad, general idea of low, medium, and high speed engines. 
9 gle cylinder high sp ral manufacturers, up to 600 r.p.m. 

I>ut -..me guide aa to practical relation between rotative 

1 



NOTES ON ENGINE DESIGN 

engine velocity, length of stroke, and horse-power the following table, made up from catalogue 
lists of twelve engine manufacturers, is given. The underlying principle compelling manufacturers 
to limit engines of such high speed as 400 to 600 r.p.m. to small sizes, is based on the stresses induced 
in the engine by the inertia of the reciprocating parts, which become very large and impracticable 
for the large masses required for large horse-power : 

Table 1. 



Revolutions 
per minute 


Stroke in 
inches. 


Bore in inches. 


Horse-power. 


600 
500 
400 
300 


5 

5 to 6 

6 to 8 

7 to 12 


5 or 6 

6 or 7 

6 to 10 

7 to 12 


11 to 30 
17 to 43 
27 to 64 
41 to 80 



Below 300 there are no definitely limited ranges for stroke, bore, and horse-power. 

6. It may be that certain desired combinations of data are not practical, and if so the student 
will run counter with some of these directions as he proceeds with his work. For example, one might 
select from the ranges given in paragraph (4) a number of revolutions and a horse-power not com- 
patible with accepted engineering practice as shown in paragraph (5). Another example is taken 
from the following table in which it is shown that there are certain practical limits for the velocity 
of the piston in feet per minute, for various classes of engines. 

Table 2. 



Piston speeds. 



Small stationary engines 
Large stationary engines 

Corliss engines 

Locomotives 



Feet per minute. 



300 to 500 
500 to 1,000 
400 to 750 
600 to 1,200 



In this problem engines up to 60 horse-power may be considered "small," and those above as 
"large," engines. 

Piston speed should not be confounded with rotative speed. The piston speed of a Corliss engine 
(which is necessarily a low speed engine) may be greater than the piston speed of a smaller high speed 
engine, as shown by a 36" stroke Corliss running at 120 r.p.m. with a piston speed of 720 feet per 
minute against 500 feet per minute for a five-inch stroke engine running at 600 r.p.m. In the former 
case the engine parts must be comparatively heavy and strong to resist the forces transmitted at 
each stroke, whereas in the latter case the parts are of comparatively light weight and transmit a 
smaller force at more frequent intervals. 

7. A further general guide in determining data in steam-engine design, is the generally accepted 
practice of using initial steam pressures between certain limits for various classes of engines as 
illustrated in Table 3. The underlying principles involved in making up the figures of this Table 



NOTES ON ENGINE DESK .\ 3 

is the law of expansion of steam, and its economical use, which retinites that its terminal pressure be 
low. With a single cylinder D-valve engine the terminal pressure cannot be low unless the initial 
pressure ia low. With multiple-cylinder engines the terminal pressure may be low and I he initial 
pressure high even with late cut-offs. 

Table 3. 



Initial cylinder pressure. Lbs. per Sq. in. gaugi . 



Single cx'liii ler engines 60 to 120 lbs. 

( 'ompound engines 100 to 180 lbs. 

Triple expansion engines 150 to 240 lbs. 

Locomo! ive engines l io to 200 lbs. 



The initial pressure in computing the low pressure cylinders for compound engines may I «• 
taken 20 to W lbs. 

8. The firsl direct step in determining the proportions of the cylinder may now be taken. In 
the formula, 

tt 2 P L a X 

Horse-power. = 

1 33,000 

it is necessary to find the mean effective pressure, length of stroke and the bore of the cylinder. 

With the boiler pressure assigned and the approximate cut-off determined by the specification of 

the valve in this problem (see also par. 10), the theoretical indicator card may be constructed and 

the trial mean effective pressure found. 

In constructing the theoretical indicator card it is necessary to make allowances: 

(a) In determining initial steam pressure in the cylinder, which is from to 10% lower than 

boiler pressure, or lower than receiver pressure if a multiple-cylinder engine 4 is being considered. 

For the Steam clearance, \\\\\vh includes the volume due to linear clearance (distance between 

on and cylinder head at end of stroke) plus the volume of the steam-port, and is usually taken 

from 6 to 1-' I of the volume displaced by the piston. Engines having short, straight ports and a 

long Strol 38 engine, may keep the steam clearance down Io J 2 to ;•)%. 

(c) For the back pressure, which is usually taken at 1 lb. above atmosphere in a non-condensing 
ich as the presenl problem, or at about 2 inches above condenser pressure if condensing. 

used, allow 26 inches of vacuum in condenser. 
For the amount of compression, which usually starts at 85 to 90* | of the completed stroke 
in low speed engines, and at 80 to 85^5 for high -peed engines. The underlying principle here 
olved in the determination of these figures, is based on a proper balancing by -team pressiu 
• a of the r< 

I • : bion of the theoretical card over the approximate prael ical card which has less 

due, principally to condensation, and to the wire drawing produced by the 
ively slow closing of the valves, some much more than others; and in engines improperly 
ssly maintained, to insufficient port areas, leaky surfao "Kent"«g 

• be following values: 



NOTES ON ENGINE DESIGN 

Table 4. 



Factor for Obtaining Probable Mean Effective Pressure from Theoretical Mean Effective Pressure. 



Factor 



Unjacketed cylinder, ordinary valve and gear 

Jacketed " " " " " 

special " " " 



0.80 to 0.85 

0.90 to 0.92 

0.94 



9. All the data are now available for the construction of the theoretical indicator card as shown 
in the accompanying diagram (Fig. 1) from which the theoretical mean effective pressure may be 
obtained graphically by taking the average of the lengths of the fine vertical lines shown at m n, o p, 



Boiler pressure 




Fig 1. 

q r, etc., on the diagram, or by other graphical methods, or by computation as given in "Kent," or 
by the planimeter. From this the probable mean effective pressure may be obtained and used in 
the formula given in paragraph (8). 

10. In the present problem the trial cut-off for the plain D-valve may be assumed at .55 to .6 
stroke; and in computing the port width the live steam velocity may be taken at 8,000 to 10,000 ft. 
per minute, and the exhaust at 6,000 to 8,000 ft. per minute. Trial cut-off is stated because it is 
desirable to keep the cylinder dimensions in round numbers when finally found; and as they will 
probably work out in quarters, eighths, or sixteenths of an inch when first determined, they can be 
most readily changed to whole numbers (or halves of an inch are often used in small work) by ma- 
nipulating the cut-off and thus altering the mean effective pressure, while still retaining the exact 
number of revolutions required. The final cut-off should fall between .5 and .7. The live and 
exhaust steam velocities are taken here rather high for the assigned range of steam pressures, but by 
so doing the valve travel will be kept down with the plain D-valve. 

11. Had the boiler pressure not been given in this problem the construction of the expansion 
curve could have been started at the pointy, Fig. 2, at any desired terminal pressure; then the expan- 



NOTES ON BN< UNE DESK IN 

mod line would be carried backward until it had reached the vertical through the desired cut-ofif 
point, and it- elevation at thai instant would determine the initial steam pn For* sample 

should 20 lbs. above atmosphere be the desired terminal pressure of the steam, the initial pressure 
for a valve giving .7 cut-off would be only 33 Ibs.j very little of the expanaivi | team 

would be made use of. and the mean effect ive pressure would be low, a ml an engine having unnec- 

would be required for a gives horse-power. Whereas with a valve 
cutting off ai .2 si roke it will be Been that the initial pressure is large I 1 1 5 lbs. gauge 
there is a wide range of expansion of t he steam, and t hat t he mean « ff< cl n i pr< ssure w ill be high, 
thus giving an economical engine with comparatively small bore and b1 roke for a gn en borsi -power. 
In multiple-cylinder engine specifications th< ■ may, in a broadj general way, apportion 

the total load equally among each of the cylinders; and the bore and Btroke of •■■•mh may then be 



II5JL 



.2 cut off 







determined by working backward from an assumed final tenninal pressure, the mil 
the low r\ Under being the terminal of the intern* diate after making due allowai 
een the cyiindi i 

L2. liter finding the probable mean eff< . a- in pa: I , all the data in h.p. 

are known < /.and'/. Since 2 LA piston speed for which then rally 



2 P i 
ooo 



:• various classes of engii • n in Tab B), I may qov 

I when th<- above formula may be boI^ rmined. 

rati<. of r varies from § - >wer valuei i d for th< 

out 1.2 for ordinary cas< s. This oompli .providing 



6 NOTES ON ENGINE DESIGN 

bore and stroke come out in even numbers. Sometimes half inches are permitted on the bore but 
rarely on the stroke and the student will observe this in his final specifications. 

Should the length of stroke not come out in even inches take the next larger or next smaller 
whole number according to judgment and work back to a new piston speed which should fall within 
the limits of Table 2. With the new piston speed, solve for a again and find d, the diameter of the 
cylinder. Should it come out in anything but whole or half inches take the next larger or next 
smaller half inch, if below 9"; or the next larger or next smaller whole inch, if above 9", according to 
judgment. Since the bore and stroke are now reduced to round numbers which must be retained, 
and since the horse-power and revolutions must remain as originally assigned, there is only one variable 
left and that is the mean effective pressure and its new and final value may be found by solving for 
P, where the revised values for L and a and the original values for N and h.p. are used. According 
as the revised mean effective pressure comes lower or higher, the expansion line i j of Fig. 1 may be 
lowered or raised by the method of trial and error and the necessary point of cut-off thus determined 
to give the required horse-power and speed. This final cut-off is the one to be used in laying out 
the Zeuner diagram in designing the valve. 

From the figures now obtained fill out the spaces in the statement of the following problem 
and proceed with the machine design. 



NOT] - l »\ I ,\i .1\ I I >l !SI< US 



-I I Th'\ ||. hi; \| CSM \\ > DESK .\. 

details for a steam* ngine cylind\ r having a diameU r of 
inches^ initial steam pressun lbs., revolutions per minuU 



13. Design to be made on full-size sheet D. I. Arrangements as sh< 



inchi 8, sttoki oj 

I 



A - 


a 

Plai 

r-i Chest 
















jO 










£ 
































1 . 


















h 


"^N 
















ij 


L 


J 


u 


Front Lot 
L 


iq Sect 

7 






Side 7?ar\s Sect 
F 



Fig. 3. 

ll. These notes are intended merely as suggestions in directing the work in the I drafting Room. 
Fuller descriptions may be found in the following books of reference: 
\ Manual of Marine Engineering," by A. E. Seaton. 
Manual of Machine Drawing and Design/ 3 by Low & Bevis. 

I. as >n- in Mechanical I drawing and Machine Design," by .). G. A. M 
"Machine DesigD " by Professor CJnwin. 

Steam-Engine Design," by Prof. J. M. Whitman. 
"The Steam-Engine," by Prof. Win. D. Marks. 

i Rounthwaite'e Pocket-Book of Marine EngineerJ 
ooner^s Machini Dea I ruction and Drawing 

"Kent's Mechanical Engineer's Pocket-Book." Phis l k must be kept at hand throughout 

b for ready reference. I 

l". ilae given in the several text-books for use in computation in designing frequently 

able result -'■>■ formula for a certain detail fane' cted to apply to all 

- and condition Where more than one formula is given in thea orpropor- 

aU formula and tin n own 

Where calculated results conflict with practical observations based on successful practice, 

ilculated results, and use the proportions thai are known to have givi d satisfactory 



8 



NOTES ON ENGINE DESIGN 



16. In the present problem the center-lines A B, C D, and E F of Fig. 3 are to be drawn only 
after the over-all dimensions have been determined by summing up the preliminary calculations 
from which a free-hand scale drawing must be made embodying only the broader essential features of 
each of the parts. This free-hand sketch is to be made on the computation sheets using the squares 
of the cross-section lines to determine the scale. This sketch, which is made from calculated values, 
should be critically examined to see if it looks reasonable in one's own common-sense judgment. If 
it does not, the computation should be gone over again, and if it still comes out the same, the person 
in general charge of the work should be consulted. Do not go ahead against your own judgment 
until you have to and then first fortify yourself with some authority. 

Sometimes it is not necessary or advisable to work out all parts in preliminary sketches before 
proceeding to lay down the center-lines on the design sheet. Some things may be assumed on the 
basis of previous experience, and the greater one's experience in the work in hand the quicker he may 
plan the arrangement of views. In the student's case, for example, he could quickly figure port 




Fig. 4. 



Fig. 5. 



Fig. 6. 



Fig. 7. 



Fig. 8. 



Fig. 



width, and then in sequence assume approximately the bridges and exhaust port, height of valve-seat 
above cylinder, height of valve and height of steam-chest, and so determine nearly enough to lay 
out center-lines, the distance from the center-line of the front view to the top of the front view, 
without waiting to work out all these details with precision. In the larger engines there may not 
be room to put in the full top view, or steam-chest plan, in which case one-half may be shown. 

17. It is to be noted at the outset that the illustrations given in these notes are intended to be 
suggestive rather than exact patterns, and therefore in some cases all the lines necessary for com- 
pleteness of projection are not shown. The missing lines should be provided by the student on 
his own work. 

18. In order to properly shape the cylinder head, as it will presently appear, the first step in 
the design will be to lay out the piston and piston-rod in place at the head end of the stroke. 

19. Sizes and forms for piston-rods and piston-rod ends, from which the student may choose, 
are here shown. Piston-rods are usually made of steel, sometimes of hammered wrought iron. 



20. Area of piston-rod at root of thread — a — 



■D 2 P 



f 



to resist tensile strain of steam pressure. 



NOTES l '\ EN< UNE DESK .\ 

a = area of rod at root of thtf / ■ 5000 for wrought iron, 

h diameter of piston in incl =7 • »i iteeL 

/' sto am pressure per square inch. 

There is also authority for d \ p for wrought iron. 

D 

vV 

(/, =i diameter of rod al root of thread. 

These latter formula are deduced from the expression: 

] j - h : P, from which* D \ [' 

bere taken al = 6400 for wrought iron. Hence d \ i> 

21. - body of rod = d = K D \ P. 

short-stroke engines, the value oj K ranges from 0.0169 to 0.0182. 

h 
other authority gives d = ftn^ ^ for wrought iron. 

, D 

.,,\ P for steel. 

long-etrol - with piston-rods whose lengths «■ 20 X diameter, or more, the 

following formula* may be used: 

d = 0.04 V D i wrought iron, 

d = 0.038 V D»? P for steel. / - Length of rod. 

D 

Ai; formula i> d = }s \ P. 

By taking/ = 3600 for wrought iron and 4800 for steel in the formula' in paragraph 20, due 
allowance is made for bending tendency of long piston-rods. 

In practice gine builders have found from experience that a rod l / 6 to V 7 of the 

cylinder give- satisfactory results, and it is often made bo without any calculation. 

24. The end of the piston-rod must be a perfect fit . Rods are usually tapered, or made conical 

at the end to permit easy withdrawal. With piston end having a large taper, a shoulder should be 

1 drawing in cone and splitting the piston, or piston hub must be made ext ra beavy, 

B ad '.'. 

When the piston taper run- the whole depth of the piston it may be at the rate i 
a inch per f< I Even with this taper the piston-rod is sometimes removed with difficulty and. 
»me this the piston shown in 1 - d used. 

shoulder u j " for small, and ! S " for large engines. Taper 3" to l foot on the 

diameters until diameter of OUtside Of thread ifl reached; then turn the remainder parallel. The 

rod Bhould fit with \;, " between the piston and shoulder for -mall engines, and H" tat lai 

. uneter of the piston-rod i the piston turn out from the calculation.-, para- 

graph 21, to be smaller than the shoulder diameter in Fig boulder may !»<• imbedded in 

bub of the piston, a- in Fig. 7. and the body of the rod turned down. 



10 



NOTES ON ENGINE DESIGN 



27. Rods with collar forged on, as in Fig. 7, are often used in heavy work. The conditions 
shown in Figs. 4 and 5 are used principally in very small and inexpensive work. Fig. 5 has cylindrical 
end, with piston shrunk on and end riveted. 



as to oj- 




Fig. 10. 



Fig. 11. 

28. Pistons are made in a great variety of forms, principally of cast iron and steel. Those 
shown in Figs. 10 and 11 are the most common forms for small engines. 

29. In Fig. 10, the dimensions shown are in terms of the unit, t = 0.0083 D^/P for cast iron. 







Fig. 12 



(The "unit method" of computing sizes is common in empirical design work especially in cases 
where exact knowledge of all stresses involved is not known. In this paragraph the unit is arbi- 
trarily taken as t and the thickness of metal in Fig. 10 is based on t in the ratios represented by the 



NOTES ON I NGINE DESIGN 



11 



Dumbers there shown.) D diameter of cylinder, and P initial steam pressure. This type of 
piston Is strengthened by thin webs connecting the t w « . wall-. Number <»t' webs, or ribs, ■ 0.08 
j> ■ :;i . h must also be tapped at o to remove the core, a nd a core-plug inserted. The width 
of piston Bhould check Fairly well with the resuh given by y~Dl when D is large. \ length of 

stroke in inchi 

30. In I'm-, li.: 0.0067 to 0.008 D vl'; b 0.86*; c - t; f - 0.95 J; A 2to3t The 
value of A' varies widely. It may be taken from onehalf to whole diameter of piston-rod, w hen one 
ring is used; / ■ width of packing-ring + \4 to i,V. Depth of single packing-ring may b 

: 5 >»i" width. Also A- is in practice frequently made •;.; " for diameters of I*')" and <>•. er, and 
for -mailer diameters. This type of piston is made wit h wall from / to i> anywhere from vertical 

I to 3. This form of ca.-t-imn pi-ton should not lie used for cylinders of more than 9 

inches bore. 

31. [n making the packing-ring Figs. L2 and L3),a solid rii ater than the .ha meter of 

the cylinder i> turned. Notches <i and h are cut halfway I hrOUgh, and the lengt hs made equal to 3 1 / 

X (diameter ring — diameter cylinder). The edges .ire then pressed together, and a pin driven 

through to hold it in position, while the ring IS again turned to the diameter of the cylinder, The 

pin is then removed, the ring sprung in place over the piston, and both placed in the cylinder. Packing- 
rings are also often split by a diagonal cu1 across the ring, instead of the box cut shown in Fig, L2. 

With the ordinary sprung ring %> " may !><• allowed for space l»»'t ween t he packing-ring and 
the bottom «>f g '.e piston. Steam i- Bomel ime> admitted behind the ring t<> secure pressure 

on the cylinder-wall, but has not proved very satisfactory. It ha- been found that a pressuj 
the ring of -\ tod lbs. againsl the cylinder-wall will prevent 
leakagi i of 100 lbs. 

33. In -oiii' especially for small quick-acting 
pump- - without packing-rings, on ••( closely 
turned piston, serve fairly well to prevent Leakage, by reduc- 
ing the energy of the motion of the -team a- it enter- each 

. e. This class of pi-ton is made rather wide 
not less tl. >f the cylinder. - 1 g, I 1. 

34. In the pistoi mentioned the packing-rings 

• be sprung in place. In larger engines and in more im- 
portant work the pi.-toii- are built up so as to insert and remove rings without springing, and 

permit of the use of various forms and combinations of packing-rings. 

el piston, the proportions of wliich are shown, t h D/200 \ P, 
b = 0.7 t, f = t, h = 4 to o t. Slope = 1 to 3. A follower-plate, or junk-ring, q, is bolted in place 

1 //. and the bull-ring, 0, are adjusted. The follower-plate bolts, which 
of wrought iron or steel, are secured in gun-metal nuts, shown atr, so as to prevent rusting. 
The 1 _ 1. and springs are placed in th< 

16 ind 17 show two view- of a "built-up" cast-iron piston thai oellent 

•e. The pi«l'T." h is 1 he " following-plate/' Othe ••l.ull-rinK." For I 

cyii number of ribs for such a piston 2, and the thickn< b ., \ P 




-bolts 



SRP P + K". 



ID 



300 



12 



NOTES ON ENGINE DESIGN 



37. In pistons of the built-up type the pressure springs (shown at E, Fig. 17) are spaced all 
around the piston in vertical engines; in horizontal engines those at the bottom are sometimes 
replaced by solid blocks to support the weight of the piston. In designing the piston, keep the 
weight a minimum within the bounds of safety. 

38. In selecting a piston type for vertical engines avoid one whose boss, or hub, would extend 
toward the under side, and require coring the crank-end cylinder-head around the piston-rod to 
accommodate the extended piston-boss. Such a core would fill with water and cause the engine 
"pound." 

39. With the form of the piston known, the thickness of the cylinder-wall may be determined 
and the cylinder-heads designed. 



777 n 





Fig. 16. 



Fig. 17. 



(a) 
(b) 
(c) 
(d) 



40. The thickness of the cylinder-wall must be sufficient: 
To resist internal steam pressure. 
To insure a sound casting. 

To resist strains in handling (in large engines particularly). 
To allow for reboring once or twice when worn. 

-2-= — , where S = 3,000, would resist the internal steam pressure. 



A thickness of t = 



A thick- 



ness of at least %> " should be used for any cylinder with a bore of 6" or over. 
Items (c) and (d) cannot be determined in advance. 

To cover all the above cases numerous empirical formula?, based on practical observations, have 
been devised. The following may be used as a guide in determining the thickness of the cylinder- 
wall: 

t = 0.0001 PD + 0.15 a/ZX 

t = 0.0003 PD + 0.375". 



P D P D 
2,500 3,500 



+ y 2 " 



41. The cylinder should be counterbored at each end to prevent packing-rings wearing a 
shoulder at the end of the stroke, and also to allow for reboring. The diameter of the counterbore 



NOTES ON ENGINE D3 SIGN 



13 



may be Is" greater than the cylinder diameter in small engines, and Jf" for lai The 

packing-ring should overtravel the oounterbore about M its width. 

£2. After drawing Gross-seel Ion of piston in place at head end of stroke, draw I he oounterbore 
shown at a, Fig. 18. Next calculate width of steam-port, considering the velocity of the exhaust 
Bteam as 8,000 feel per minute for engines with a bore of more than 9 inches, and 6,000 feet per 
minute for 9-inch bore or less. Make the length of port :; t diameter of cylinder. The point c of 




V m 



Fig. is. 



the port may be taken directly over b, or a small distance to the right, c d = width of steam-port 
-f %>" to allow for friction of steam on the rough-cast port surface. Make the thickness of wall e 
equal to cylinder-wall. 

43. Lay off d f = 1.5 X thickness of cylinder-wall. / then lies in plane of cylinder-flange 
surface. This is generally made flat the whole width of the flange, ss Bhown, and some form of 
gasket used to make the joint steam-tight. Another plan is to make the flange surface about W 
wide radially from /and make a steam-tight joint without gasket by BCraping. See illustration in 
Fig. 22. The value Y% " is taken because flaws in wbichmighl happen to come on such a 
faced surface, are not, as a rule, more than Z A" . Beyond the scraped joint the rough-cast surfaces 
of the flanges may each he set back ±/ 32 " on small engines, and }&" on larger ones. 

44. The thickness of the cylinder-wall flange may be 1.25 t«> 1.5 X thickness of cylinder wall. 
The metal taken at a for the counterbore m ing made OOl*- 
ventionally equal to the diagonal of a square h.i\ ing the thifiknftSfl <•!" the cylinder wall for its sides. 



14 



NOTES ON ENGINE DESIGN 



45. The width of the cylinder-flange, x y, Fig. 18, depends on the size and kind of bolts used. 
Through bolts require a wide flange to make room for head, or' nut, under the cylinder-wall; they 
also cut into the " lagging " (wood or metal covering usually placed on cylinder between flanges). 
Felt, asbestos, or other non-conducting substance, is placed between lagging and bare cylinder- 
wall, to prevent undue radiation of heat. Stud-bolts are generally used. The size and number of 
these should be so chosen : 

(a) that a working stress of not more than [(area at bottom of thread) 5 / 12 X C] per square inch 
falls on them. (C = 5,000 for wrought iron or mild steel); 

(b) that the distance between their centers (measured on the bolt circle) should be about 5 or 6 
diameters apart, in order to hold the cylinder-cover flange firmly to its seat and prevent escape of 
steam between the bolts. 

Cylinder-bolts less than %" in diameter should not be used, except on very small work, on 
account of liability to excessive strain by wrench in screwing up the nut. 

A shop rule sometimes used, is to make the diameter of the bolt = y 2 (thickness of cylinder 
flange X thickness of cylinder-cover flange). The cylinder-cover flange may be made 1.15 to 1.25 
times the thickness of cylinder-wall. 

Some authorities give one bolt for each inch of diameter, but this gives a rather larger number 
than is found in the latest practice. 

46. The tap for stud-bolt in cylinder-flange may be made about flush with the cylinder-wall, as 
shown at h, Fig. 18. With the position and diameter of bolt thus shown, the radius of the bolt 
circle is determined. With a standard nut on the bolt, and an allowance of }4" at k I, the minimum 
width of cylinder-flange is known. The cylinder-flange width is often made 3 bolt diameters. 

47. The cylinder-head flange, y I, Fig. 18, has a thickness of about 1.15 to 1.25 X cylinder-wall, 
and should always be less than that of the cylinder-flange y m, for, in case of accident, the latter 
is the more difficult and costly to replace. In some shops the stud-bolts are weakened by a groove 
so that the bolts will break instead of the flanges in case of accident. 

48. The inside line of the cylinder-head must conform with the outline of the piston as closely 
as possible, to keep down the engine clearance, which is the volume inclosed between the piston and 
the cylinder-cover at the end of the stroke + the volume of the ports. 

49. The piston clearance is a linear distance between the piston and the cylinder-head at the 
end of the stroke, and is necessary to allow for wear in the two connecting-rod ends and in piston- 
rod end; also for roughness of casting of the cylinder-head and piston-walls. From ^ to %" is 
sometimes allowed for the latter, and %>" for each of the three working joints in horizontal engines 
of the sizes in this problem. The following is a reliable table for piston clearance in vertical engines: 



Piston Clearances for Vertical Engines (for horizontal engines use head-end clearance for both ends) 



Diameter of cylinder. 


Head end. 


Crank end. 


Up to 14" ' 


Vs" 

V*' 
%" 

K" 

%" 

X" 


v%" 


15" " 20" 


l /2" 


21" " 40" 


%" 


41" " 60" 


M" 


61"" 80" 


Vs" 


81" "100"... 


%" 


above 100" 


1" 







SOI ES ON I \< ilNE DESK A 15 

50. The thickness of the cylinder-cover between the flanges maj be made to that of the 
cylinder-wall for smaller engines. ( overs for medium-sized engines maj have the same thick] 
strengthened bj radial ribs on the outside, or they may be cast hollow, as shown in Fig. 18, if the 



H h— 0.55 



0.45 



H V— 055 




l to, 19. 






piston formjpermits. Covers for large cylinders are always made hollow with internal stiffening 

ribs. 

51. RgB. L9 and 20 show cylinder-heads with principal proportions for large cylinders. The 
figures given arc in term- of the unit . 

52. The cylinder-cover for the crank end may next be constructed. Here, also, the inside 





Wiq. 21. 






16 



NOTES ON ENGINE DESIGN 



line should follow the piston contour at a distance equal the piston clearance. In small engines 
the crank-end cover may be cast solid with the cylinder-wall, as shown in Fig. 21. When this is 
done the opening, a, should be large enough to admit the boring-bar in turning or truing the cylinder. 
When the stuffing-box is a part of the removable cylinder-cover, as in Fig. 22, the size of the opening 
at a for the purpose of admitting a boring-bar need not be considered. 

53. With the cylinder-wall and cover cast in one piece, as in Fig. 21, the flange is added just 
the same. It is necessary for bolting the cylinder to the engine-frame. 

54. The cylinder-cover shown in full lines in Fig. 22 may be made as a hollow casting by 
adding the wall shown in dotted lines. 

55. The piston-rod stuffing-box may now be designed. In Figs. 23 and 24, S is the stuffing-box, 
G the gland, and B, B, B are bushings. 

56. Figs. 23 and 25 show two distinct methods of detail for stuffing-box construction, only one 
of which the student should adopt. The piston-rod is not allowed to come in contact with the cast 
iron on account of rust forming when the engine is still any length of time, and injuring the rod. 




Fig. 25. 



Fig. 23. 



Fig. 24. 



The solid "brass-," or gun-metal gland in the lower-half design of Fig. 23 is used on smaller engines, 
and on increasing sizes up to the point where the cost of necessary brass is less than the cost of the 
smaller amount of the same metal used in the upper-half bushing plus the cost of the iron gland 
and the machining of the same. 

57. For low-pressure engines the space E around the piston-rod is filled with greased hemp 
rope, asbestos, or various other brands of compressible packing. Numerous patent metallic pack- 
ings are on the market, and are coming into general use, especially for high-pressure engines. Hemp 

and similar packings are not serviceable under high temperatures. 

58. The small bushing B in the upper half prevents the packing from entering the cylinder. It 
is not continued through the cylinder-cover, as is the bushing in the lower half. The latter is 



NOTES i'N i:\< IINE DESIGN 



17 



largely used, although some maker- object to it on the ground thai the small neck is apt to break 
off and fall into the cylinder, thus damaging the cylinder-wall and piston. This may be prevented 
by the construction shown in Fig. 25, the tapered bushing being made a little too long at first, and 
thm riveted over Into the countersink formed In the cylinder-cover, The thickness of the 03 Under 
r at K ranges from the value at // in small engines to t be value of b for larger work. The depth 
of bushing at g may be taken about 2 >n. 

59. Definite rules cannot be given for stuffing-box proportions thai will suit under all circum- 
Btan< quently the designer makes the packing Bpace to suit the size of a BpeciaJ brand of 

metallic packing that has proved satisfactory. The following tabulated data, and formula? given 
in paragraphs 60 to 63 for the more important dimensions, represent good practice: 



Diameter 


Width of 


1 >epth of 
packing. 


Depth of 


Thickness 


Number and 


of 


packing 


neck 


of 


diameter 


rod. 


space. 


ring. 


bushing. 


of bolts. 


d 





/ 


9 




No. x 






1 






2 K" 


1" 




2" 






2 W 




"A" 




H" 


'." 


2 


li -." 


1 " 

1 


2>/' 


\" 


'." 


2 




1 ' a 




IX" 




2 


• >" 






IV 


'." 


2 


2X" 


%•• 




1H" 




- 


2M" 






1-," 




* - 

X" 


2%" 


H" 


4" 


m" 




2 1 
|3 


3" 


X" 


±X" 






1 2 1 

I a 


*X" 


%" 




w 




• 
1 3 : ~ 






5" 


2" 




j 2 r 

1 3 1 



In the table on this page the values of a are based on a Bolid gun-metal gland. With cast-iron 
glands hushed with gun-metal a must be increased I ^ " in each case. For hemp packing, and piston- 
rods under l 1 ," diameter the following rule for a may be Used: 

a = X d + J£" or H". Take m equal to a, or a little less. 

GO. Fig. 23, b = % d + H" [minimum), e - IX to! A. rule for the 

diameter of the stud, x, 18 H d +,] _•"• Draw the bolt, X, with the thread- flush with the si llffing-box 
wall, thus permitting the flange to be made narrower. The studs are often forged with hexagonal 
collars, as shown, for convenience in screwing in place, and for bearing Burfaoe when jamming the 
thread. A circular collar is sometimes used for the latter pun" -• Frequently these stud- 
made without collars, to save expense, in which case the Beat ing of the nut depends on the jamming 
of the end thread. 



18 



NOTES ON ENGINE DESIGN 



61. The diameter, or length, of the stuffing-box flange may be such that the line ate falls a 
distance x + V& " to M " from the center-line of stud. Length of gland n = % to V 5 /. The distance 
the gland may be moved in should be y to % f so that the packing may be compressed or taken up 
by this amount if desired. Thickness of gland-flange, e, when of brass or composition metal should 
be equal to c, as shown at h; when of iron, it should be less than c, lli x or M d + Z A" giving fair 
values. The lock-nuts should have a combined depth of ly x. In practice they are used in two 
ways: 1st, one nut is of standard depth, and the other nut y 2 standard depth; 2d. both nuts are 
of the same depth — Z A x. The last method is preferable. In every case the nuts are of standard 
diameter, to permit use of standard wrenches or spanners. 

62. The end view of the stuffing-box and gland, Fig. 24, shows a common form of the same. 
k = y 2 d + g, + b + Y%" to M". If the form of the stuffing-box gland is made circular, as it fre- 
quently is, it may receive a finish by turning at the same time the cylinder-flange is turned, with 
very little extra expense. The surface for the form shown in Fig. 24 must remain rough cast, or 
have a more expensive hand finish. The gland-flange may be made a trifle smaller than the stuf- 
fing-box flange, as shown. Very often the stuffing-box flange and gland-flange are made circular 

in which case three stud-bolts are generally used, each bolt having a diameter of about x x = '. — 

X (0.12 d + 0.4"). N = number of bolts used. (See Fig. 27.) 

63. Fig. 26 shows one-half of a stuffing-box using a popular metallic packing consisting of metal 
rings. The small spaces form annular recesses for collection of water due to condensation. A 






Fig. 26. 



Fig. 27. 



fibrous ring is placed between the gland and packing to facilitate lubrication. With this style of 
packing the value n in Fig. 23 may be considerably less, as there is comparatively little compression 
of the packing. 

64. After designing the stuffing-box, the height of the valve-seat may be determined. This 
should be as close to the cylinder-wall as possible, in order to save both space and weight in the 
cylinder casting. Its minimum elevation is governed by the necessary sectional area in the exhaust 
passageway at x } Fig. 29, leading to the exhaust-pipe B. Sometimes the position of the eccentric 
on the shaft (which should be in line with the valve-stem), requires that the elevation of the valve- 
seat should be greater than that called for in the previous sentence: in this design the latter point 
need not be considered. Before determining the minimum value of the cross-section, x, the width 
of the exhaust-port, a b, Fig. 28, should be known. This distance depends upon the exhaust-lap of 
the valve, which must therefore be laid out at this point of the design. 



NOTES ON l.\< IINE DESIGN 



19 



65. Const met a plain 1) slide-valve that will give the i beoreticaJ indicator card already drawn, 
paragraph 8. Take lead ,' ." on engines of 9" diameter and under, and V," <»n all over. In 
this exercise both ends <>f t lit- valve may be made symmetrical. Should the exhaust-lap come oul 
negative, change it arbitrarily in this problem to sero andeorred the indicator card accordingly. 
Thia change will ordinarily do! effect the mean effective pressure beyond the range of allowances 
already made. Assume that connecting-rod equals five crank lengths. 

Lay down the valve-seat , Q &, at a trial elevation and draw a trial COntOUT tor the exhauM 

port . a g h f>. thus determining a t rial average widt h. .... This work should be Light ly drawn, as t be 
following consideration may make a change necessary. 







29, draw the center-line of the exhaust-pipe, /»'. bo that when produced it 

tot! of the cylinder-wall. When the above and following directions hav irriedout, 

and the height of tl it determined, it will be observed t hat to draw this center-line higher 

would raise the b, and that to draw it lower would require that the exhaust ; <y, x, 

I farther around the <•> Under-wall, thus cooling it and aiding condensation in the cylinder. 



20 NOTES ON ENGINE DESIGN 

68. Next calculate the area of the exhaust-pipe so that the steam velocity in the pipe shall be 
from ^ to M of the velocity through the port. Check-rules for this diameter are: (1) That the 
area of exhaust-pipe should be 50% greater than the area of the steam-port; (2) That the diameter of 
the exhaust-pipe should be about Yz the bore of the cylinder. Look up in "Kent," under " Pipes — 
Wrought Iron/' and find the thickness and outside diameter of exhaust-pipe determined upon, and 
then draw in place, as shown in Fig. 29. In marine work, especially where copper pipes are used 
on account of their flexibility, the exhaust-pipe boss is flanged, as shown by dotted lines in Fig. 29, 
and the pipes are flanged correspondingly and bolted fast. For proportions of this flange, number 
of bolts, etc., see "Kent." 

69. The horizontal line through i may be drawn about X& " above the pipe thread so as to allow 
clearance for pipe tap. Draw the edge line of the port, k j, and round off the corner with the arc 
j i. Measure the radial distance, x, of the smallest section at this point, and multiply by y, its average 
width as obtained in paragraph 66. This should give an area = 1.33 X steam-port area. If it 
should be lacking only a small amount, x may be increased by using the dotted arc, t u, with center 
at q, as the outline of the cylinder. If it is still too small, another trial height of valve-seat must be 
taken so that lines a g and b h will spread more and give a greater value to y. 

70. The steam-chest may be cast solid with the cylinder on smaller engines, or may be, espe- 
cially in larger ones, cast separately and bolted down. The plan of the steam-chest may be rec- 
tangular, as shown in Fig. 30, or it may be circular. In either case the opening under the steam-chest 
cover must be large to allow putting the valve in place. The steam-chest walls on all sides may be 
placed as close to the valve-seat center as the valve-travel will permit, and the flange placed entirely 
on the outside of the wall; or, the walls may be so placed as to have the flange outside on two sides 
and inside on two sides, as shown in Figs. 28 and 29. Sometimes the flanges are placed on the 
inside of all four walls. Note that allowances for placing the steam-pipe should be made in planning 
the walls and flanges of the steam-chest. The valve, when in its extreme position should not be so 
close to the end of the steam-pipe as to obstruct the flow of steam. 

71. The thickness of the steam-chest walls may be made the same as the cylinder-walls, or if 
the latter have been taken rather heavy the chest-wall may be thinner. The flanges may be 25% 
greater than the cylinder-wall. The steam-chest cover flange may be made slightly less than the 
chest-wall flange, and the steam-chest cover equal to or a little less than the chest-wall. The rules 
for width of flange, and diameter and number of bolts for the steam-chest, are based on the same 
principles which apply to the cylinder and cylinder-cover flanges. Sometimes the thickness of the 
steam-chest flange may not figure equal IK times stud-bolt diameter, which is necessary to give the 
latter a proper hold. Then a boss may be cast on the under side of the flange, as shown in dotted 
lines for the bolt, o, in Figs. 29 and 30. 

72. The steam-chest cover may have a drop-seat of from % " to M ", as shown in Figs. 28 and 
29. This is desirable in serving as a guide inasmuch as the bolt holes in the steam-chest cover are 
larger than the bolts. The height of the steam-chest may be such that the distance between the 
top of the valve and the under side of the steam-chest cover equals, at least, the width of the steam- 
port. 

73. In case the steam-chest wall in Fig. 28 is drawn closer to the valve-seat and the flange 
placed outside, the faced surface, p, for the seat of the screwed valve-stem stuffing-box must be moved 
out to the end of the flange in order that the stuffing-box nut, /, Fig. 31, may be conveniently 
accessible in screwing on. 



NOTES ON I NGINE DESIGN 



■_'l 



74. The diameter of the vab 31, ma) be found by taking the total load on the 

valve- ! / length, b breadth of valve, and p initial steam pressure), and multi- 

plying by a coefficient of friction, which in cases of this kind is bakes as high a- 20 or -•">' , dui 

• io start valve, especially after a period of Idleness. The strain of the valve-stem at the root of 
the threads should uot exceed 2,600 lbs. per square Inch for 1<>ii- wrought-iron rods of small diami 
and 3,500 lbs. for steel. Forengini 9 I ' bore and ordinary length of rod,3, 

lbs. may be used for wrought iron and 5,000 lbs. for steel, Having calculated the nee 




n 


= 






9 


- 


M 


d + ' » 


k 


= 


?* 


<l. 




= 


21 





the root of the thread, the outside diameter may be readily found in the table on " I Hers 

System of Screw-Threads," in "Kent." In practice the- diameter of the valve-rod will be usually 
found tobeH to '_> that of the piston-rod if both arc made of the same material. 

75. The valve-stem stuffing-box is usually made of brass, and screwed in place, see Fig. 31. 
The following proportions for the box, gland, and bushings may be used: 

a = 1 H d. b = 2 d + ; r. 

e = 1 Kd. f = <l + V". 

h - 2 d + M j - 2 d + H 

I = lHd. /// = M (L 

-■ proportions give a long stuffing-box, which has the advantage that the packing does not 
require f " be very I ightly compressed. When circumstances require it, this length may be reduced. 

76. The type of stuffing-box shown in Fig. 31, although used principally on the valve-rod in 
engine work, is sometimes used also for the piston-rod. Instead of the hexagonal form the gland 

metimes made circular with bngitudina or sometimes with radial holes, in either 

otresponding form of spanner being used to screw up the gland. 

77. The steam pipe may be placed as shown in Fig. 28 at .t . or in large engines I he steam-chest 
may be » i T c and bolted to the engine cylinder. The diameter of the pipe may be cal- 
culated, using a steam velocity at least equal to that used in computing the steam-port. A rough 
rule in practice is that the steam-pipe should be about ! [ the cylinder-bore. 

78. In finishing t he design, place on t he necessary working dimensions and indicate the finished 

surfaces. 



ini) i ■: .\ 



Allowance for boring l>ar in cylinder-head m» 

Allowance for wear \.\ 

Arrangement of views 7. 8 

exhailSl -port width 10 



B 

Hack pressure 3 

Boiler pressure, range of 1 

Boh*. t\>r cylinder-flange 14 

Bolts for pistons 11 

Bolts for steam-chest flange ' 20 

for stuffing-boxes 17, [8 

listance between centers 14 

Bolts, empirical rules for 14 

grooves turned in 14 

minimum size of 14 

Bolts, workii - n 14 

I reference 7 

bar allowance in cylinder-head 16 

• n cylinder flange 20 

Built-up pistons 11 

Bull-rings 11 

Bushings [6, 17. 21 



Castings, flaws in 13 

Center-lines, locating 8 

Changing data to vary slightly the cylinder 

dimensions 6 

Circular stuffing-box flanges 18 

Clearance, engine and piston 14 

Clearance, steam and linear 3 

Clearance, table of piston, or linear 14 

Compression, amount of • 3 

ting-rod length 10, 

11 

Corliss engine, piston velocity of -? 

Counterbore 1-'. [3 

Crank-end cylinder-cover 10 

trial and final 4, 6 

Cylinder diameter and Stroke-length g 

Cylinder-flange, location and form of 13, 18 

( ylinder-head flange thickness 14 

Cylinder head for crank end 15 

Cylinder-head, shape and location of 8 

Cylinder-head, thickness of 15. 17 

Cylinder-wall thickness 12 

Cylinder, reboring of I-' 

(Minder, size of 3 



D 

Data f. >r draftsman's design 7 

Data for engi 1 

Design of steam-engine 1 



I. 

Economy of engine 1 

Engine clearance u 

Engine, selection of type of , ■ 

Engineer's design 1 

. large and small .. . . 

Engines, low, medium, and high speed 1 

Exhaust-lap, negath e 10 

Exhaust-pipe, location and area ), 20 

Exhaust-port, width of 18 

Expansion line 



Factor for finding probable m.e.p.. \- 6 

Final cut-off 

Finishing the draw ins 21 

Flange, location and Form of cylinder-flange 

face 13 

Flanges for exhaust -pipe 20 

Flanges t""r steam-chest 20 

Ranges for stuffing-box and gland [8 

Raws in castings i\ 

Follower-boll sizes 11 

Follower-plate 1 1 

Formula tor body of piston-rod 9 

Formula for cylinder-wall thickness u 

Formula for horse-power 

Formula for piston-rod at ro.,t of thread 9 

Formulae for piston parts 10 

Formulae for short and long rods 9 

Formulae, conflicting 7 

Free-hand drawing to scale 8 

Friction of starting '>i valve 



G 

Gasket 13 

Glands, forms and sizc> of t6 l8, -'I 

in pistons 11 

turned in bolts 14 



II 
I [eight of steam chest 

I [igb speed - ngines 1 

. formula for . , ...3 

power, range of . . 1 



I 

Indicator card, apj ...3 

Indicator card, theoretical 

Initial St< am pressure 

Initial than boiler-pressui 



24 



INDEX 



Junk-ring 



PAGE 
. II 



L 

Lagging 14 

Large engines 2 

Lead for different engines 19 

Leaking past packing-rings 11 

Length of port 13 

Limiting speed 2 

Linear clearance 3 

Location of exhaust-pipe 19 

Location of live steam-pipe 20 

Location of valve-stem stuffing-box 20 

Lock-nuts 18 

Locomotives, piston velocity 2 

Low-speed engines I 



M 

Mean effective pressure, probable 4, 15 

Mean effective pressure, revised 6, 19 

Mean effective pressure, theoretical 4, 5 

Medium-speed engines 1, 3 

Metallic packing 16, 18 

P 

Packing, compressible 16, 18 

Packing, metallic 16, 18 

Packing-ring construction 11 

Packing-ring sizes 11 

Packing, width and depth of 17 

Paper to use for calculations and sketches 8 

Piston and rotative speeds 2 

Piston clearance 14 

Piston grooves •■. 11 

Piston velocity 2 

Piston-rod positions 8 

Piston-rods, forms and sizes of 8, 9 

Pistons for vertical engines 12 

Pistons, forms and sizes of 10, 11 

Port, length of 13 

Practical indicator card 3 

Pressure in packing-rings 11 

Pressure, initial 2 

Pressure, range of 1 

Pressure, terminal 2 

Probable mean effective pressure 5 

Proportions for high-speed engines 2 



Ratio of initial to terminal pressure 1 

Reboring cylinders 12 

Reference books 7 

Relation between bore and stroke length 5 

Relations between r.p.m., stroke length and h.p..i, 2 
Relative thickness of cylinder and cylinder-head 

flanges 14 

Revised mean effective pressure 6 

Revolutions per minute, range of I 

Ribs for pistons, number and thickness of 11 



PAGE 

Rotative speed of engines 1 

Round numbers for cylinder sizes 6 

Rust, arrangement of parts to prevent ... 16 

S 

Scraped joints 13 

Selection of type of engine 1 

Single cylinder high-speed engine 1 

Size of cylinders 4, 6 

Size of drawing paper 7 

Sketch, free-hand 8 

Small engines 2 

Speed, high, low, and medium 1 

Speed, rotative 1 

Spider 1 1 

Steam-chest 20, 21 

Steam-chest cover 20 

Steam clearance 3 

Steam-engine design 1 

Steam-pipe, size and location of 20, 21 

Steam-port, size and location of 13 

Steam-pressures, limits for different classes of 

engines 2 

Steam-tight joints 13 

Steam velocity, live and exhaust . . 4 

Stuffing-box for piston-rod 16-18 

Stuffing-box for valve-stem 20, 21 



T 

Table of factors for probable m.e.p 4 

Table of initial steam pressures 3 

Table of piston or linear clearances 14 

Table of piston velocities 2 

Table of stuffing-box proportions 17 

Table showing relations between r.p.m., length of 

stroke and h.p 2 

Taper of piston-rod ends 9 

Tapered bushing 17 

Terminal steam-pressure 3, 5 

Theoretical indicator card 3 

Thickness of cylinder-cover 15, 17 

Thickness of cylinder-cover flange 14 

Thickness of cylinder-flange 13 

Thickness of cylinder-wall 12 

Thickness of steam-chest cover and cover-flange. 20 

Thickness of steam-chest wall and flange 20 

Trial cut-off 4 

Trial valve-seat and exhaust-port 19, 20 

V 

Valve, construction of 19 

Valve-seat, location of '. . 18, 19 

Valve-stem diameter 21 

Valve-stem stuffing-box 21 

Velocity of exhaust steam 4, 13 

Velocity of live steam 4 

Velocity of piston _ 2 

Vertical engines, pistons for 12 

W 

Wear at joints 14 

Width of cylinder-cover flange 14 

Width of cylinder-flange 13 



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LBJa'12 



